Domain report: nbn-resolving.de

Registration

info

.de country-code

Found

TLD: .de (country-code)
ICANN policies apply: no

Checks

i

.de is a country-code TLD (ccTLD)

Country-code TLD: governed by its local registry under national policy, not by an ICANN contract. Registrar accreditation, dispute resolution and RDAP/WHOIS rules are set by the registry.

#1
✓ TLD delegated and signed #2

.de is delegated in the root zone and DNSSEC-signed.
i

Registration data not available

No registration data via RDAP: the registry of .de offers no RDAP service. Many ccTLD registries don't offer RDAP; check the registry's WHOIS instead.

#3

Delegation

info

dns-1.dfn.de, ns0.dnb.de, ns1.dnb.de

Found

Parent zone: de
Delegation from: a.nic.de (194.0.0.53)
NS at the parent: dns-1.dfn.de, ns0.dnb.de, ns1.dnb.de
NS in the zone: dns-1.dfn.de, ns0.dnb.de, ns1.dnb.de

Nameserver	Addresses	Network (AS)	Glue
dns-1.dfn.de	193.174.75.50 2001:638:d:b101::1	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	-
ns0.dnb.de	193.175.100.253	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	193.175.100.253
ns1.dnb.de	193.175.100.254	AS680 DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE	193.175.100.254

Checks

✓ 3 nameservers #6

Delegated to dns-1.dfn.de, ns0.dnb.de, ns1.dnb.de.
✓ Parent and zone agree #7

The parent delegation and the zone's NS records list the same nameservers.
✓ No glue needed #8

All nameservers are outside the zone, so no glue records are needed.
✓ All names resolve #9

Every nameserver name has an address and is not an alias.
✓ Nameservers in different networks #10

The nameservers are spread over 2 IPv4 /24s and 1 IPv6 /48.
i

All nameservers in one AS

All nameserver addresses are announced by one network operator (AS680 (DFN - Verein zur Foerderung eines Deutschen Forschungsnetzes e.V., DE): 4 addresses). An outage or attack on that network affects all nameservers; large anycast providers mitigate this, but a secondary DNS provider adds independence.

#11
i

All nameserver names under .de

All nameserver names are under one TLD, so a problem with that TLD also makes the nameservers unreachable. Some operators use names under two TLDs for extra resilience.

#12
i

Partly IPv6

These nameservers have no IPv6 address: ns0.dnb.de, ns1.dnb.de.

#13

Nameservers

fail

2 of 4 addresses answer authoritatively

Found

Nameserver	Answer	Recursion	TCP / EDNS	AXFR	Version
dns-1.dfn.de 193.174.75.50	NOERROR, 14 ms, authoritative	no	yes / yes	refused	0
dns-1.dfn.de 2001:638:d:b101::1	NOERROR, 14 ms, authoritative	no	yes / yes	refused	0
ns0.dnb.de 193.175.100.253	no response	no	no / no	-	-
ns1.dnb.de 193.175.100.254	no response	no	no / no	-	-

Checks

✗

Nameservers not responding

These addresses did not answer, so resolvers waste time on timeouts: ns0.dnb.de (193.175.100.253): read udp 46.225.38.91:60940->193.175.100.253:53: i/o timeout; ns1.dnb.de (193.175.100.254): read udp 46.225.38.91:59520->193.175.100.254:53: i/o timeout.

#14
✓ All authoritative #15

Every responding nameserver answers authoritatively for the zone.
✓ No recursion #16

The nameservers do not answer recursive queries for other domains.
i

Identifying string disclosed

These nameservers answer version queries with a string that is not a version number: dns-1.dfn.de: "0".

#17
✓ Zone transfers refused #18

No nameserver allows a zone transfer to the public.
✓ TCP supported #19

All nameservers answer over TCP.
✓ EDNS supported #20

All nameservers support EDNS(0).
✓ Public addresses #21

All nameserver addresses are publicly routable.

SOA

warn

serial 2026091516 · primary ns.dnb.de

Found

Primary (MNAME): ns.dnb.de
Contact (RNAME): hostmaster.dnb.de
Serial: 2026091516
Refresh / retry: 3600 s / 3600 s
Expire: 2419200 s
Negative TTL: 3600 s

Serial per nameserver

Nameserver	Serial
dns-1.dfn.de (193.174.75.50)	2026091516
dns-1.dfn.de (2001:638:d:b101::1)	2026091516

Checks

✓ Serial 2026091516 everywhere #22

All nameservers serve the same version of the zone.
!

Unusual SOA timers

retry 1h should be shorter than refresh 1h. Current values: refresh 1h, retry 1h, expire 28d, negative TTL 1h.

#23
i

Hidden master (not resolvable)

The primary nameserver ns.dnb.de is not listed as a nameserver and does not resolve publicly: a hidden master, or a placeholder name. Some tools (e.g. dynamic updates) use MNAME to find the primary.

#24
✓ Contact hostmaster@dnb.de #25

The SOA RNAME hostmaster.dnb.de means hostmaster@dnb.de.
✓ Date-based serial #26

The serial 2026091516 follows the YYYYMMDDnn convention (2026-09-15).

DNSSEC

warn

Signed, DS published at parent

Found

Validated by resolver: yes
Denial of existence: NSEC3
NSEC3: 100 iterations, 8-byte salt
Signatures valid until: 4 November 2026

DS at the parent

Key tag	Algorithm	Digest	Matches a key
41780	RSASHA256 (8)	SHA256 19E8B38365281EA9…	yes

DNSKEY in the zone

Key tag	Role	Algorithm
41780	KSK (257)	RSASHA256 (8)
40810	ZSK (256)	RSASHA256 (8)

Checks

✓ Signed and validated #27

The zone is signed, the parent publishes a DS record, and the resolver validates the answers.
✓ DS matches a key #28

The DS record at the parent matches a key in the zone: key tag 41780 (SHA256).
✓ Modern algorithms #29

Key algorithms: RSASHA256 (8).
✓ Signatures valid until 2026-11-04 #30

The earliest DNSKEY/SOA signature expires at 2026-11-04 23:27 UTC.
!

NSEC3 with extra iterations or salt

NSEC3 uses 100 iterations and a 8-byte salt. RFC 9276 recommends 0 iterations and no salt: extra iterations cost resolvers CPU and add no real protection, and some validators treat high counts as insecure.

#31

Records

warn

12 records at the apex

Found

Read from: 193.174.75.50:53

Type	Value	TTL
SOA	ns.dnb.de. hostmaster.dnb.de. 2026091516 3600 3600 2419200 3600	60
NS	ns0.dnb.de.	60
NS	dns-1.dfn.de.	60
NS	ns1.dnb.de.	60
A	193.175.100.226	60
MX	10 mail.dnb.de.	60
TXT	"HARICA-uU9Fb4kbtMjnuYgTIR4"	60
TXT	"HARICA-80HLk8lyad7ikko9S8G"	60
TXT	"HARICA-ZNSbTWiIdeDvCAPgWFz"	60
CAA	0 issue "harica.gr"	60
CAA	0 issue "sectigo.com"	60
CAA	0 issue "pki.dfn.de"	60

Checks

!

Very low TTLs

These records have a TTL below 5m, causing extra queries and slower lookups: A (1m), MX (1m), NS (1m). Low TTLs are useful just before a planned change. The NS TTL at the parent is 1d and in the zone 1m; resolvers may use either.

#32
✓ No CNAME at the apex #33

The zone apex has no CNAME record.
✓ No wildcard #34

Names that don't exist return NXDOMAIN.
✓ CAA restricts issuance #35

Certificates may be issued by: harica.gr, sectigo.com, pki.dfn.de.